Tuesday, September 21, 2010
The Heavy Glider
An intimate look at the Shuttle Orbiter
Because of the delta wing and elevon pitch controls, the Orbiter takes a bit of getting used to in the flair—the initial response to a pitch increase is an increase in sink rate, so the pilot needs to plan ahead and be patient with corrections. Trying to make an acceptable touchdown even better usually results in PIO, with a wild gallop down the runway and a fervent hope that the initial touchdown will be at the right spot in the oscillation. Touchdown conditions are largely determined by how you’re set up crossing the threshold, and sweetening things up (as we all do in conventional airplanes) is generally a bad idea. Setting up that point on the inner glideslope is far easier with the head-up display (added in the 1980s) than it was in the early days. The fact that you have to make the landing work without a go-around eventually gets pushed to the back of your mind.
In the late ’80s, as we recovered from the loss of the Challenger, I was part of a team developing improvements to the landing and deceleration systems for the Orbiter—better brakes, tougher tires, redundant steering actuators and the new drag chute. We spent countless hours flying landings to a full stop in various simulators, tweaking the software and developing procedures that led to a more robust vehicle. The drag chute development was especially exciting as we tried different sizes, attach points and reefing schemes to make it effective without lifting the Orbiter back off the runway when it had already run out of sufficient airspeed for control. Using a simulator made the rides exciting without being expensive—the only thing damaged in the inevitable hard landings that come with test flying were our egos. Out of that effort, we developed the confidence to add shorter runways to our catalog, giving ourselves additional options for aborts on ascent and emergency landing sites in case problems arose later in the mission. The Shuttle system became more flexible, enabling longer and more complex missions, such as the assembly of the Space Station.
In the three decades that the Space Shuttle fleet has operated, tens of thousands of dedicated men and women have played countless key roles to make over 130 missions both safe and successful. Every one of them has stories that weave a great tapestry telling the tale of America’s reach into what we call “low Earth orbit (LEO).” While we often hear that the public is bored with the “same old thing” (going back and forth to the Space Station and doing science), the truth is that there are no boring missions, and we’re operating at the very edge of human engineering capability every time. Margins are usually razor-thin in order to make the overall system light enough to achieve the necessary performance, and they leave little room for error.
Flying the Shuttle has been both a career and an adventure. Most of the people who have been involved would probably tell you that they would have done it for free, just to be a part of it. For the pilots among us, there’s nothing to match the exhilaration of continuing the long expansion of the speed and altitude envelopes that began with the Wright Brothers’ 6.8 mph, 120-foot-long (and a few feet high) flight. The early X-planes of the ’50s led to the X-15 of the ’60s—and many of the techniques and trajectories that we know and use today in the Shuttle can be traced directly to that program. All of those thoughts run through my mind as I slip into the left seat of the simulator one more time, and ask for the 50,000-foot reset point, hanging motionless above the desert of California. Rogers Dry Lake lies just under the nose, the lake-bed runways beckoning as they’ve done for countless landings of experimental machines.
As I call for the simulator to be taken to “run,” I turn off the HUD, take the speed brake to manual, open it 50%, and roll into a steep turn with the runway in sight out the left window. The descent rate might be an order of magnitude more than I grew up with, but the Shuttle is still an airplane—a glider—that responds to a pilot’s touch. Every once in a while, it’s good to remember that and fly the machine by hand, eye and feel. The lake bed is large, and has been a beacon to many who have gone before—pilots stretching to enlarge the sphere of aeronautical knowledge and experience. Higher, faster and farther has always been the goal—and while programs come and go, the dream remains. Aviation is about exploring, and even for those of us who really are “airplane guys,” our destination is the stars.
Paul Dye is the lead flight director for NASA Human Space Flight, served as a flight director on 37 Space Shuttle missions and flies an RV-8 that he built.
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